1. Field of the Invention
The present invention is concerned with improvements in and relating to a method of mounting a door in an automobile body structure.
2. Description of the Prior Art
Japanese Patent Laid-open Application (unexamined) No. 63-17190 discloses a method of mounting a door in an automobile body structure conveyed along an automobile body assembling line. In the method as proposed in this disclosure, a reference pin mounted on one of two vertically spaced hinges is initially inserted into a reference hole formed in that portion of the body structure on which the hinges are to be fixedly mounted. The door is then rotated a predetermined amount about the reference pin for proper positioning thereof. Finally, both the hinges are rigidly secured to the body structure by means of bolts.
This method requires a reference pin mounted on one of the hinges and a reference hole formed in the body structure, thereby increasing the number of manufacturing operations or working processes. As a result, there arises the problem that efficiency of the door mounting operation is reduced.
Furthermore, the door is clamped by a material handling jig mounted on a robot arm. Accordingly, even though the door is properly positioned prior to the mounting thereof in the body structure as mentioned previously, the door generally has a tendency to move downwardly due to the weight of the door when the material handling jig releases the clamping thereof. As a result, there arises the problem in that the door slips downwardly from a proper location thereof. The reason for this is that the hinges have respective gaps for permitting the movement of the door, thereby producing looseness.
In positioning the door, the amount of rotation thereof about the reference pin can be determined based upon a measurement in which the vertical position of a door-position detecting portion provided in the door is determined through an image processing operation. However, when the door is slightly open, measurement errors occur in the vertical position of the door-position detecting portion, thus resulting in improper positioning of the door.
More specifically, in some recent automobile body structures, generally vertically spaced hinge pins for pivotally mounting a door therein are not coaxially aligned with each other but are inclined so that opposed ends thereof may be directed forwardly or rearwardly for the purpose of smoothly opening and closing the door. This recent trend, resulting in installation errors due to visual sensors (cameras) and the like, cause errors in the vertical position of the door in accordance with the amount of opening thereof at the time the door is mounted in the body structure.